Light emitting diode (LED) is a kind of semiconductor diode that can transfer electric energy into light energy and emits visible light in yellow, green, blue and the like as well as infrared and ultraviolet invisible light. LED is characterized by low working voltage and current, high reliability, long service life and ease of luminance regulation, etc.
The traditional LED chip is driven by the direct current (DC). Therefore, to ensure normal operation of the LED, a rectifier transformer is required for AC/DC transformation when the supply power is alternating current (AC). In addition, power saving performance is of great importance to LED applications. However, the traditional LED's efficiency is still unsatisfactory since AC/DC transformation may consume as high as 15%-30% power; under this background, an LED directly driven by AC comes into being.
FIGS. 1-3 show a current AC-type LED. According to FIGS. 1-3, two LED units 210 and 220 are arranged on a substrate in the same direction. Strip-current extended electrodes 410 and 420 and a bonding pad connect an n-type layer of a first LED unit 210 to a p-type layer of a second LED unit 220 and connect a p-type layer of the first LED unit 210 to an n-type layer of the second LED unit 220, thus constituting an AC-type light emitting element. However, the single LED unit of the AC light emitting element has a lateral structure, while the lateral structure LED chip cannot be driven by high current density owing to low light emitting efficiency, current blockage, high thermal resistance, etc.